Note: Rhythm game, Touhou and/or IOSYS haters beware.
I would say it seems like it could be a real freeware game, but it seems too good to be true.
After looking at some Samba De Amigo videos (and eventually jumping from rhythm game to rhythm game), I found this. It looks like a simple freeware video, but the reason I doubt it to be real, is because so far, it's the only video of it I've seen. Plus, something this different would have spread around the internet eventually.